This invention relates to an air release valve.
Air release valves are installed in liquid reticulation pipelines and serve to vent to atmosphere gases entrained with the liquid conveyed in the pipeline. One known type of air release valve is described in the specification of South African patent 88/3478. In this case there is a closure member which seats on the valve outlet under pressure conditions and which is formed with a small bleed orifice that vents accumulated air under the control of a control float.
While the valve described in patent 88/3478 has been shown to work extremely well in practice, it suffers from a drawback that is experienced during filling of the pipeline. The situation is that the closure member is lifted dynamically to seat on the valve outlet as air rushes out of the valve. Air can then only vent slowly through the small orifice and the process of pipeline filling is slow.